The present invention relates to a remote control unit for controlling through telephone lines an additional device coupled to a telephone set, and more particularly relates to such a unit wherein the user, having controlled the wrong additional device by sending a wrong remote control signal to the devices, can, without hanging up the telephone, control the correct device by sending the correct control signal.
Different types of nontelephone system additional devices tend to be attached to a telephone system in recent years. For example, a facsimile system connected to a telephone set generates an off-hook signal upon ringing once or twice irrespective of the will of the calling party and starts facsimile operation without going through a speech state, thus confusing the calling party. When an additional device other than the facsimile system is connected to the telephone set, the speech communication by means of telephone sets is also neglected, and the operation of the nontelephone system additional device has a priority over telephone communication, resulting in inconvenience.